Compound air-compressor.



bio-830,503. PATENTED SEPT. 11, 1906. E. HILL.

7 COMPOUND AIR COMPRESSOR.

APPLICATION FILED AUG.18,1905.

. THE HDHRIS PETERS 00., WASHINGTON. u. c.

cleaning heavy articles.

UNITED sr rns EBENEZER HILL, or NORWALK. C( HK COMPOUND AIR-COMPRESSOR.

Specification of Letters Patent.

Patented. Sept. 11, 1906.

Application filed August 18, 1905. Serial No. 274,657-

To all whom it may concern:

Be it known that I, EBENEZER HILL, a citizen of the United States, residing at Norwalk, in the county of Fairfieldand State of Connecticut, have invented a new and useful Compound Air-Compressor, of which the following is a specification.

It is desirable to build air-compressors so that with a single machine air may be supplied at widely-different pressures for various uses. They are often desired for use in mines for supplying air at comparatively low pressures for operating drills and other tools and for supplying air at very high pressure for driving locomotives. In manufacturing establishments it is desirable to be able to supply from a single compressor air at high pressure for pneumati ctools,-hoists', and general power purposes and at low pressure for sand-blasting, painting, blowing chips, and In the interest of economy and efli-ciency in operating the various inchanisms it is necessary that the pres sures used be constant.

This invention relates to an air-compressor which is designed to supply air at two different pressures.

The object of the invention is to provide a very simple and eflicient construction whereby air may be supplied from a single compound compressor at two widely-different pressures which will remain practically constant under the various conditions of use.

The invention resides in a compound compressor having a valve in the duct between the low-pressure cylinder and the high-pressure cylinder which automatically closes the passage through the duct when the low-pressure piston does not supply a sufficient quantity of air at the desired pressure for both the low-pressure use and the demand of the highpressure piston, thus without interrupting the reciprocation of the high-pressure piston preventing that piston from drawing air from the duct between the cylinders and lowering the pressure in the pipe from which the air at low pressure is being drawn for use.

Figure 1 of the drawings shows a side elevation of so much of a compound air-compressor as is necessary to illustrate the invention. Fig. 2 shows, on larger scale, a central section of the valve which is arranged in the duct between the high and low pressure cylinders to automatically choke the supply of air for the high-pressure cylinder when air at low pressure is being drawn from the duct.

:The first or low-pressure cylinder 1 and the second or high-pressure cylinder 2 are of ordinary construction, and they have the usual inlet and outlet valves and pistons of the common compound compressor. Air is taken into the low-pressure cylinder through the intake 3 and forced throu h the interduct 4 to the high-pressure cylin er, from which it is forced through the discharge 5 to the highpressure system. Air for low-pressure use is drawn from the interduct through the pipe 6, i

and in the interduct between the point where the low-pressure air is drawn off and the highpressure cylinder is a choke-valve 7-that is, a valve which is arranged so as to stop or hinder the flow of air from one cylinder to the other under certain conditions by entirely closing or restricting the air-passage. v

The choke-valve shown has two ports 8, movable in which is a balanced valve that consists of two connected disks 9, which are provided with guiding-spiders 1.0. The stem 11 of this valve is connected with a small piston 12, that moves in a cylinder 13, which opens to the inlet side of the valve. A spring 14 is arranged to thrust against the piston in such manner as to tend to force the valvedisks into the ports. A thumb-screw 15 is arranged in the cap 16 that closes the outer end of this cylinder for regulating the tension of the spring.

When the low-pressure system is being used, the choke-valve closes the passage through the interduct to the high-pressure cylinder. If the lowpressure system is not being used, the choke-valve remains open, so the air will flow freely-from the low-pressure cylinder to the high-pressure cylinder. When. air is drawn from the interduct for low-pressure use, the first effect is to lower the pressure in the interduct. This drop of pressure lessens the pressure on the choke-valve pisders arranged to open and close the passage through the duct according to the ressure in the duct between said valve an the lowpressure cylinder, substantially as specified.

2. The combination in a compound compressor of a low-pressure cylinder, a highpressure cylinder, a duct connecting the discharge of the low-pressure cylinder with the intake of the high-pressure cylinder, a valve adapted to close this duct, means for drawing air from the duct between said valve and the low-pressure cylinder, means controlled by the pressure in the duct between the valve and the low-pressure cylinder for opening and holding open said valve when the pressure in the duct between the valve and the low-pressure cylinder is normal, and means acting in opposition to the pressure for closing and holding said valve closed when the pressure in the duct between the valve and the low-pressure cylinder is below normal, substantially as specified.

3. The combination in a compound compressor of a low-pressure cylinder, a highpressure cylinder, a duct connecting the discharge of the low-pressure cylinder with the adapted to close this duct, means for drawing air from the duct between said valve and the low-pressure cylinder, a piston connected with said valve and subject to the pressure in the duct between the valve and the loW- pressure cylinder, and a spring arranged to thrust the-piston in opposition to said pressure, substantially as specified.

4. The combination in a compound compressor of a low-pressure cylinder, a highpressure cylinder, a duct connecting the discharge of the low-pressure cylinder with the intake of the high-pressure cylinder, a balanced valve 4 arranged to close this duct, means for drawing air from the duct between said valve and the low-pressure cylinder, a piston connected with said valve and subject to the air-pressure in the duct between the valve and the low-pressure cylinder, a spring thrusting against the piston in opposition to the air-pressure and means for adjusting the pressure of the spring, substantially as specified.

EBENEZER HILL. Witnesses:

J. E. SLATER, H. H. MOSSMAN. 

